Lehrstuhl für Computergestütztes Planen in der Architektur
Fakultät für Architektur / RWTH Aachen

Solar Decathlon 2012

(Counter-Entropy House)

Logo für das Solar Decathlon Projekt 2012

Entropy: ˈen-trə-pē

A measure of the unavailable energy in a closed thermodynamic system that is also usually considered to be a measure of the system's disorder and that is a property of the system's state and is related to it in such a manner that a reversible change in heat in the system produces a change in the measure which varies directly with the heat change and inversely with the absolute temperature at which the change takes place - broadly : the degree of disorder or uncertainty in a system.


The attempt to locally reverse the tendency to disorder described in the definition of entropy; creating order from chaos; creating value from the invaluable.


Climate change is, in most circles, an accepted fact and the call to action, or to change our actions, has reached all aspects of our society, planning and construction included. Nonetheless, the acknowledgement that our activities must make a noticeably reduced impact on the environment does not necessarily entail knowing which ways are the most effective. Construction accounts for a very large part of the environmental impact of our daily activities and so it is natural to focus on the building industry, in order to reduce these impacts. In the past years, this has largely concentrated on the energetic needs of the building industry, particularly in the heating and cooling of dwellings and workplaces.

To some extent, the easily attainable efficiencies in heating and cooling have been made, at least in the laboratories. Many older buildings still need to be retrofitted, usually with better insulation and more efficient heating and cooling systems. However, once these changes have been made, it is quite difficult to further increase the efficiency of buildings. Indeed, many buildings can reach a zeroenergy state, where no additional energy from the electricity network is needed to run the building. In fact, research is being conducted into energy-plus buildings, where the building itself produces more energy than is needed to run it.

This sounds all well and good, except that most of the "plus" energy is not generated by the house itself, but rather by the addition of ancillary technologies such as photovoltaics or wind turbines. As such, these so-called energy-plus houses merely act as scaffolds for a plethora of energy generating devices. To be sure, they are energy efficient - however, the impact reduction of the building itself is not necessarily better just because the photovoltaics are better.

What is more, in a complete life-cycle assessment of the environmental impact of the house (LCA), the environmental costs of production, erection and indeed disassembly also need to be accounted for. This is also the case for ancillary technologies should they contribute to the operational energy balance of the house.

Embodied Energy

Buildings consume energy not only in their operation, but also in the manufacture of the building components, in the transport of the components to the building site and in the assembly of the components into a finished building. This is not a small amount of energy. Furthermore, the erection of a building involves large masses of materials that are found within the building components themselves or in the production of the components. This energy (as mass or as energy spent to erect the building) is the embodied energy within the building. This energy and mass must be taken into account in performing energy balance calculations of any building.

Our goal is to greatly reduce the amount of embodied energy not necessarily within the building, but necessary to produce it. This is an important difference as the decision to build does not start 1000 years ago. Rather it starts today and as such, we have the chance to use existing materials, components and other "already embodied" energy. This can be done in several ways, which we will explore and demonstrate in our competition entry.

In short, we are attempting to follow a doctrine of re-use, but at several scales and levels of granularity. By re-using existing embodied energy, we can greatly reduce the embodied energy needed to produce the building. Our goal would be to create an "Embodied-Energy-Plus" house alongside the "Energy-Plus" signet used to describe the operational efficiency of the building.


The principle to re-use and re-cycle can be seen at several levels, but inherent at all levels is the idea, to produce less chaos and entropy than existed before the building was built. At the simplest level, this can mean using easily recyclable materials in the production of the building components. In some cases (e.g. steel production), a relatively high rate of recyclable materials already exists. In other cases, the recyclability is either in its infancy or has not yet been explored.

At the other end of the spectrum of Re-Use is the chance to re-use old building components in new buildings. This was often limited, due to the inefficiency of older components (e.g. single paned windows) or the way components are assembled (e.g. PVC foam and other glues inhibit the ability to cleanly separate the components). Nonetheless, there are many types of building elements that can be easily reused, particularly in the interior construction (e.g. parquet flooring) and the fixtures (e.g. door handles).

The real advantage though, comes through the re-use of components that are partially recycled but with improved efficiency (e.g. new glazing in old window frames) or through the use of fabricated products and materials in ways for which they where not originally intended - this is often called upcycling or super-use. In effect, by using elements that would normally be considered waste (and often end up in land fills) we can use the embodied energy without having to produce new elements and furthermore, reduce the waste or entropy in general - hence the name of our entry: the Counter- Entropy-House. And by constructing the building with the intent of re-use (e.g. prohibiting glues and Solar Decathlon Europe 2012 - RWTH Aachen University 2 foams as connections between elements), we will allow the further use of the buildings parts, thus furthering the principle of counter-entropy.

Main Objectives Of The Team

The overall objective of the competition entry is to make a decisive contribution in each of the competition categories with the aim of being named as one of the more successful entries. In addition to the Solar Decathlon evaluation criteria, the team has set further goals that adhere to the doctrines and aims of the Counter-Entropy-House.

Zero Energy

The goal of the competition entry is to adapt known efficient technologies for the operation of the building. We do not attempt to create an energy plus building as we are not convinced, that over and above the local needs of the individual buildings, it is meaningful to place large amounts of energy generation on buildings. For example, photovoltaics are really only effective in certain climates and machines like windmills impose a threat to life and limb should mechanical failure ensue. Nonetheless, the operational performance of the building should achieve high efficiencies in energetic needs for heating, cooling and ventilation.

Zero Embodied-Energy

A major goal of this competition entry is to demonstrate that efficient technologies for the operation of the building are not enough to claim that a building is ecologically sound. By placing the complete energy and mass-flow balance at the forefront of our project, we hope to encourage debate about mass flows and embodied energy in buildings. Our goal is to erect a zero-embodied-energy demonstrator, which, through the incorporation of diverse recycling, re-use and super-use directives, will show how the erection of buildings need not necessarily entail the huge energy and mass flows that have until now been the case.

Zero Entropy

Under the imperative: „Plan Globally - Source Locally“ we also hope to demonstrate how design principles can be adapted to local building customs and codes, but also to local sources of building elements - either through recycling, re-use or super-use. As such, the realisation of our plan will optimise in as far as possible, the use of local materials in the competition entry and thereby minimise the total transport costs of the building. We are quite sure that all the competitors will incur these environmental cost, but not include them in their calculations.

Low-Tech - High Impact

The counter-entropy principle entails using the latest technologies when they bring significant gains in efficiency or in the re-use of materials. Should this not be the case, tried technologies or even artificially simple solutions will enable the project to still achieve efficiencies in operation and a significantly small ecological footprint.

Materials are the Message

Reusing building components made of recycled materials or reusing building elements cannot negate the ecological impact that is predetermined once the decision to build has been made. It can however alleviate the ecological impact by exporting the embodied energy outside the system boundaries of the ecological balance calculations. It is also possible, through the demonstration of re-use and superuse directives, to shift the discussion of "green buildings" from the operational efficiency to one of complete life-cycle analysis and calculations with the hope to show the potential and the challenges that are involved in up-cycling materials for buildings.

It could be said that the goal of a "zero-emission" building is only meaningful once we have been able to create a "zero-production" building.

Zeitraum: 2011 - 2012


Solar Decathlon Europe


Lehrstuhl für Gebäudetechnologie


  • Professor Dr. Dirk Müller